In minerals separation processes for the concentration of a mineral from a low grade ore, one of the most important methods is flotation. The method is based upon the selective separation of components in an aqueous medium by causing one or more of them to float above the slurry of pulverised ore and water. There is added to the slurry a flotation agent or frother, and a collector, under agitation. The frother causes formation of bubbles or froth, which rise to the surface of the aqueous slurry, and the collector aids in causing contact between the particulate solids and the froth, so that the solids of the mineral which it is desired to separate attach to the froth and float on top of the slurry. The type of collector chosen depends upon the nature of the mineral it is desired to separate.
Calcite (CaCO.sub.3) a low grade ore, is ore, is found along with many more valuable minerals, but is in many instances particularly difficult to separate from other minerals by a froth flotation process. For example, calcite is found in conjunction with the valuable tungsten ore scheelite (CaWO.sub.4). However, serious difficulties have been encountered in separating and concentrating these two materials, since they both float together in froth flotation processes previously practiced. Although calcite can be eliminated from the mixed concentrate of these materials by acid leaching, such a process is too expensive for economic use on a commercial scale. The separation of calcite from scheelite is thus a major and difficult process step in producing high yields of scheelite.